Anchorage device



Patented Nov. 6, 1934 1,980,093 ANCHORAGE DEVICE Heyman Rosenberg, NewYork, N. Y.

Original application January 16, 1925, Serial No. 2,874. Divided andthis application May 13,

1925, Serial No. 30,008

2 Claims.

This invention relates to improvements in the art of anchorage and inanchorage devices of the type especially adapted for use in metal andother hard substances and materials susceptible of be- 5 ing flowedwhile cold. This application is a division of my parent applicationSerial No. 2,874, led January 16, 1925.

An object in view is the causing of the flow of the material of work bysuccessive steps into ay l compact, high-frictional relation to theengaging parts of an anchorage device for insuring rm anchorage incidentto the application of relatively small stresses.

A further object in view is the effecting of an l anchorage with aminimum amount of stress and `with maximum eiiiciency.

With these and further objects in view as will in part hereinafterbecome apparent and in part be stated, the invention comprises certainnovel steps and combination of steps in the art of anchorage, and alsocomprises certain novel constructions combinations and arrangements ofparts as subsequently specified and claimed.

In the accompanying drawing,-

Figure 1 is, a view in side elevation of an anchorage device especiallyWell adapted for the practicing of the improved art, and embodying thefeatures of the structural part of the present invention, the structurebeing shown in engagement with work, and the work being seen in verticalsection, the parts being shown on a magniiied scale beyond that of theaverage commercial device. Figure 2 is a horizontal section taken on theplane indicated by lines 2-2 of Figure l, and

looking along the screw toward the head.

Figure 3 is a view similar to Figure 1 of the parts with the anchoragedevice only partway through the work, the upper portion of the anchoragedevice being omitted.

Figure 4 is a sectional view through the work after the anchorage devicehas been fully seated and subsequently removed.

Figure 5 is a. view similar to Figure 1 dfn slightly modied embodiment,the work being omitted and fragments of the anchorage device beingbroken away. y

Referring to the drawing by numerals, 1 indicates the body of ananchorage device which is preferably cylindrical and provided at itsentering end with a smooth or pilot portion 2 of greater diameter thanthe diameter of the main portion of the body, the body terminating in apoint or entering. cone 3. At the opposite end, the body 1 is preferablyprovided with an appropriate head 4, such as that of the ordinary screw,having the kerf 5 for receiving a rotating instrument. The body 1 isprovided with a ribl made up of a section 6 and a section 7, each ofsaid sections being preferably of a length approximately equal to thethickness or depth of the work 8, or at least equal to the distancethroughout which the anchorage device is to engage the work when in itsseated position. The 'rib making up the sections 6 and 7 in theembodiment shown in Figure 1 is arranged on a thread spiralcorresponding with that of an ordinary wood screw thread and extendsfrom the pilot 2 to the head 4. The rib is hardened in the sense inwhich the term hardened is employed in the metallurgical art todistinguish from soft metals, which is to say that the thread or ribmaking up the sections 6 and 7 is hardened suilciently for enteringmetal, such as soft iron or soft steel, substantially without injury tothe thread. The method of hardening the thread or rib making up thesections 6 and 'l is susceptible of a wide range of variation, but forordinary commercial purposes the hardened condition is preferablyattained by subjecting the whole anchorage device to a case-hardeningprocess, such as the well known cyanide process. The hardening of theother parts `of the 'structure beside the thread is an incident to suchprocess, and While adding little, if any, value to the completedstructure in no sense detracts therefrom and aiords an inexpensive meansof producing a hardened thread.

As will be clear from the dotted showing at the intermediate portion ofthe anchorage device, as seen in Figure 1, the sections 6 and 7 arealined, and, in fact, continuous of each other, the thread or rib ofsection 6 tapering into the thread or rib of section 7, it beingapparent from Figure 1 that the thread or rib of section 'l outstandsfrom the body 1 a less distance than the thread or rib making up section6. In other words, the rib for section 'l is smaller and of lessdimensions in every direction except length and spacing between helicesthan is the thread or rib making up section 6. ,The thread or rib making`up sections 6 and 7 is a continuous spiral of uniform and substantiallylow pitch. The dimensions of therib or thread making up section '7 arethe same, that is, uniform, throughout the length of the section, andsimilarly the thread or rib making up section 6 has its dimensions thesame, that is, uniform, throughout the length of the section, andvariation in dimensions occurs only at the point of junction of the '110only sufliciently larger to allow passage of the4 pilot therethroughwith a snug t. lli'he anchorage device is applied by the introduction ofthe point 3 into the opening 9, the taper of the point facilitating andassisting in centering the anchorage device and bringing the pilot 2intoaxial alinement with the opening 9. The pilot is then passed intothe opening with a longitudi- :nal thrust of the anchorage device untilthe entering end of the rib or thread of section 'lI engages the upperpart of the work 8. The anchorage device is then revolved whilepreferably subjected to stress in the direction of its length toward thework 8, as, for instance, by having `the kerf 5 engaged by ascrew-driver and the anchorage device revolved thereby. Thethread ofsection '7 begins to enter the metal of work 8, severing the same andforming a passageway therein similar to internal threads, and therevolving operation continues until the pilot 2 has passed through thework 8. course, that as soon as the thread has sufficiently entered thework, the longitudinal stress may be no longer required. It will beobserved from the showing in Figures 1 and 3 that during the Asteps ofthe operation thus far described, the ithread or rib making up section 7will have caused the metal of work 8 to flow to a position overhangingthe annular shoulder at the upper end of the pilot 2 resulting from thefact that the pilot 2 is larger in diameter than that of the body 1. Theowing of the metal of work 8 thus effected causes it to enter thevalleys bee tween the helices of the rib and to frictionally engage thefaces of the rib. Nevertheless, since .the rib or thread making up'section 7 is of rela- ,tively shallow depth, the twisting stress necessary for forcing the anchorage device into the .Work 8 is comparativelysmall.

When the anchorage device has reached the position with the pilot 2extending beyond the work 8, the thread or rib will have reached thatpoint at the upper surface of the work 8 where it tapers from theenlarged rib of section 6. However, as the internal thread produced bysection '7 is completed before section 6 begins to enter, continuedrotation of the anchorage device will cause section 6 to enter the Workwith very little, if any, additional force or torsional stress requiredthan that required for the introduction of section 7. Continuedrevolution of the anchorage device causes the thread or rib of section 6to enter the material 8 and to proportionally increase the internalthreads being formed therein until they assume the proportions indicatedin Figure 4, the metal entered by the larger rib or thread being causedto ilow thereby to a greater extent toward the body 1 than was effectedby the action of the smaller section of thread or rib until the materialof the work.8 extends in toward the body 1, as indicated at 10, 10, inFigure 4, a distance occupying substantially all of the spacerepresented by the It is obvious, of,`

difference in diameter of the opening 9 and the body 1, whereby thematerial of work 8 is caused to practically ll the valleys between thehelices of section 6 and to proportionally increase frictionalresistance to removal of the anchorage device. The anchorage device can,of course, after reaching the final seated position with the section 6extending throughout the thickness of the work 8 be backed olf by areverse or withdrawing rotation, but such rotation will be highlyresisted by the friction effected by the flowed metal at 10, 10.

It will thus be seen that -in a very simple manner the anchorage iscaused to assume a relation to the work without the exercise of anygreat amount of stress which it will maintain under all ordinaryoperating conditions.

In Figure 5 is illustrated a very slight modified l embodiment in whichthe body 21 is provided with a low-pitched thread or rib formingsections 26 and 27,.the rib for the section 26 being of greaterdimensions than the rib for section 2'7 land tapering into the latterafter the manner of the taper of the rib or thread making up section 6into the rib or thread making up section 7. But, in the embodiment seenin Figureg, the body 21 is itself tapered at the place of tapering ofthe thread, producing a reduced portion 22 which causes the thread ofsection 27 to have approximately the same relation to that part of thebody which it engages as has the thread of section 26 to its part ofbody 21. Where ay pilot is employed, the pilot willbe of a diameterbearing that relation to the body 21, or larger diameter of the body ofthe anchorage device, which pilot 2 bears to body 1. The operation ofthe structure seen in Figure 5 is the same as that describedwith'respect to the structure seen in Figure 1, except that in instanceswhere metal may be caused to ow by the rib or thread 27 far enough tounderhang the larger portion of the body, such flowed material iscompressed by the body on reaching and passing the point of such flowedmaterial, and an increased frictional engagement is thus effected.

Because of the difficulty of accurately illus trating so small astructure as the average commercial anchorage device, a magnifiedscalehas been utilized throughout the drawings, and yet, for the purposeof enabling those skilled in the art to understand that the proportionshave been as nearly as practically maintained in these mag niedshowings, it may be stated that an acceptable embodiment will have anoverall longitudinal measurement of one inch; a diameter for the pilot 2of one hundred thirty-two thousandths of an inch; and the body 1 onehundred eighteen thousandths of an inch. A. circle capable'of contactingat diametrically opposite points with projected diametrically oppositepoints of the edge of a helix of rib or thread 7, that is, such a circleas seen in Figure 2 representing said helix, in a structure of the sizejust mentioned should measure in diameter one hundred forty-sixthousandths of an inch, and a corresponding circle for a helix of rib orthread 6 should' have a diameter of one hundred seventy-four thousandthsof an inch. In other words, an anchorage device having an overall lengthof one inch should have a pilot one hundred thirty-two thousandths of aninch in diameter, a body 1 one hundred eighteen thousandths of an inchin diameten' a thread or rib.'7 outstanding from the body at any onepoint a maximum of fourteen thousandthsof an inch, and a thread or rib6.out-

standing from the body at one point a maximum of twenty-eightthousandths of an inch.

Obviously, a wide range of variation from these measurements is clearlywithin the spirit, intent and scope of the invention, but the foregoingwill give definite data for indicating the preferable lrelativeproportions, and it should be noted that while only two sections, 7 and6, have been illustrated, a number of such sections successivelytapering into each other may be utilized for increasing the diameter ordiametrical space occupied by the final engaging rib or ribs withoutsubstantially increasing the difficulty or stress necessary for locatingthe anchorage device in its final position.

It should also be apparent that in the practicing of the art embodyingthe present invention the material of the work is severed in a spiralpath and caused to flow in an encircling mass toward the body of theanchorage device, and then, While the anchorage device continues tomove, the flow is interrupted; and subsequently the encircling mass isfurther flowed toward the bOdy.

body and a single continuous thread of constant pitch outstandingtherefrom hardened suii'lciently for entering metal, such as soft ironor soft steel, substantially without injury to the thread, said threadcomprising' alined and joined sections of geometrically similarcross-section, each section outstanding from the body a constantdistance and being of substantially uniform cross section within its ownlimits throughout its length, the section adjacent the entering end ofthe body outstanding a less distance than the HEYMAN RosENBERG.

